Force sensor systems of the above-described type are used, for example, for determining the flatness of strips while they are processed in strip processing lines or roll stands.
Measuring rolls are used in the cold rolling of various types of sheet metal strips or film strips, wherein the strip is guided under tension over a measuring roll with a certain wrap angle and said measuring roll determines the distribution of stresses of the strips over their width by means of sensors integrated into the roll. Such measuring rolls typically feature a plurality of sensors that are arranged in radial bores of the measuring roll that are open toward the roll surface with high prestress or positioned in axially parallel bores closely underneath the surface of the measuring roll.
Alternatively, a clamping sleeve may also be clamped over the roll. EP 0433535 discloses a prestressing element that generates the desired prestressing force by means of an adjustable wedge. This force sensor system is characterized in that the prestressing force amounts to a multiple of the strip force to be measured.
External heating of the measuring roll due to the hot strip may cause a deformation of the roll geometry of the measuring roll and therefore lead to a change of the prestress. The changed prestress causes the measuring sensitivity of the sensors to change accordingly such that the previously measured calibration values are no longer correct.
WO2004/065924 describes a prestressing element for such a force sensor, and WO03/061856 also describes the prestressing devices, as well as the type of installation.